Charge coupled device with meander channel and elongated, straight, parallel gate electrodes

ABSTRACT

A charge coupled device has a meandering charge path formed by a channel stop of unique shape. The channel stop is of interdigitated pattern, and the gate electrodes form a straight strip. The channel stop pattern and an asymmetric depletion layer formed within the channel cause the transfer of the charge through the channel via the meandering charge path. A transversal filter and imaging device are readily provided by extracting the signal from one or both sides of the channel.

BACKGROUND OF THE INVENTION

This is a Continuation application of application Ser. No. 332,241,filed Dec. 18, 1981, for Charge Coupled Device, amended to ChargeCoupled Device With Meander Channel and Elongated, Straight, ParallelGate Electrode, issued as U.S. Pat. No. 4,531,225 on July 23, 1985which, in turn, is a Continuation of application Ser. No. 887,655, filedMar. 17, 1978, for Charge Coupled Device, and now abandoned, and which,in turn, is a Continuation-in-Part of application Ser. No. 735,639,filed Oct. 26, 1976, for Charge Coupled Device and now abandoned.

The present invention relates to a charge coupled device. Moreparticularly, the invention relates to a semiconductor charge coupleddevice having a meandering charge path.

A charge coupled device is hereinafter referred to as a CCD.

The conventional charge coupled device usually has the same number ofbus lines as the phases of transfer pulse trains and each gate electrodeis respectively connected to any of such bus lines. Since the bus linesare usually formed on a semiconductor or substrate with insulating filmused for separating them, electrostatic capacitance, that is MOScapacitance, exists between the bus lines and the substrate. When thesize of the electrode becomes small, the capacitance of the bus linesbecomes comparable with the sum of the capacitance of the electrodes.The load of the clock pulse generator used as the transfer pulse sourcethus becomes heavy.

Furthermore, in a CCD in which the gate electrodes are arranged on thesubstrate surface in the shape of a matrix consisting of rows andcolumns, electrodes forming a group arranged in a direction, forexample, in the direction along the columns, are connected and alwayskept at the same potential. It is therefore impossible to permit eachrow to perform the transfer operation individually. Any attempt toindividually drive each row of such a CCD results in very complicatedwiring patterns, because of the need for a bus line to be arranged foreach row, and results in low integration density. Moreover, when a lineaddress is carried out by using the CCD as a memory device, individualtransfer for each row is necessary. However, the foregoing facts aredisadvantageous for a line address.

The principal object of the invention is to provide a charge coupleddevice which overcomes the disadvantages of known types of similardevices.

An object of the invention is to provide a charge coupled device ofsimple electrode structure.

Another object of the invention is to provide a charge coupled devicewhich is simple and inexpensive in manufacture.

Still another object of the invention is to provide a charge coupleddevice which is readily converted to a transversal filter or imagingdevice.

Since the CCD of the invention has gate electrodes in the shape ofstraight strips, the manufacturing process may be simplified and eachline may be easily individually driven when many lines are arranged inparallel. Furthermore, since the signal may easily be extracted from aside or both sides of the charge path, due to the meandering chargetransfer route, the CCD of the invention may be readily utilized as atransversal filter or line image sensor or imaging device.

BRIEF SUMMARY OF THE INVENTION

The present invention is a CCD having a meandering charge path anddevices using such a CCD. The CCD of the invention has an interdigitatedchannel stop or stops formed on the semiconductor substrate surface. Themeandering charge path may be established by the channel stop or stops.The cells of each CCD are staggered. Typically, the gate electrodes areformed in the shape of two straight strips. On the other hand, a meansfor forming an asymmetrical depletion layer such as, for example, anon-uniform thickness of the insulating film is added to each cell. Whentwo pulse trains having different phases relative to each other areapplied to the two strip electrodes, the signal charge is transferred tothe longitudinal direction of the charge path over the meandering route.

In accordance with the invention, a charge coupled device comprises asemiconductor substrate of predetermined conductivity type. Thesubstrate has a surface. A channel stop is formed on the substratesurface and has a pair of substantially band-shaped portions extendingin spaced substantially parallel relation. The channel stop comprises ahigh impurity concentration layer of the predetermined conductivity typeformed on the substrate surface. A charge transfer area is bounded bythe band-shaped portions. A plurality of short channel stop portionsextend from each of the band-shaped portions toward the center of thecharge transfer area. Each of the short channel stop portions terminatesat a predetermined space from the band-shaped portion toward which itextends. The short channel stop portions are spaced from each otheralong the length of the device and thereby form a meandershaped chargetransfer route in the charge transfer area. Less than threesubstantially strip-shaped linearly extending gate electrodes extendsubstantially parallel with the band-shaped portions of the channel stopin the charge transfer area.

The channel stop and short channel stop portions form an interdigitatedpattern.

The short channel stop portions typically extend substantiallyperpendicularly from each of the band-shaped portions in spacedsubstantially parallel relation with each other. The short channel stopportions extending from each of the band-shaped portions aresubstantially equidistant from each other along the length of thedevice. The short channel stop portions extending from each of theband-shaped portions are substantially equidistant from the shortchannel stop portions extending from the other of the band-shapedportions.

Insulating means is interposed between the substrate and the gateelectrodes for insulating the gate electrodes from the substrate.

An asymmetrical depletion layer or layers is or are formed in the chargetransfer area between next-adjacent short channel stop portions. Thecharge transfer area has sides. At least one projecting portion extendsfrom the channel stop at a side of the charge transfer area. Signalinput and output means are provided in the projecting portion orportions. A regenerative amplifier amplifies an extracted signal chargeand returns the amplified signal charge to the projecting portion.

Next-adjacent gate electrodes forming a pair are spaced from each otherby a gap. A film of electrically insulative material covers the gateelectrodes and fills the gap between the gate electrodes. A conductivelayer is provided on the film of insulative material over the gap.

Next-adjacent gate electrodes forming a pair are spaced from each otherby a gap. The substrate is of predetermined conductivity type. A regionof opposite conductivity type from the predetermined conductivity typeis provided on the substrate surface, just below the gap.

Next-adjacent gate electrodes forming a pair are spaced from each otherby a gap. A semiconductor layer of high resistivity fills the gap andcontacts both electrodes.

A film of electrically insulative material covers the substrate. Theasymmetrical depletion layer is formed by a partial difference in thethickness of the film of insulative material covering the chargetransfer area.

A photosensitive portion or portions is or are provided at the center ofthe charge transfer area. The meander-shaped charge transfer route isprovided on both sides of the photo-sensitive portion and themeander-shaped charge transfer route on both sides of the photosensitiveportion transfers the charge generated in the photosensitive portion.

In accordance with the invention, a transversal filter comprises asemiconductor substrate having a surface. A channel stop is formed onthe substrate surface and has band-shaped portions extending in spacedsubstantially parallel relation to each other. Each of the band-shapedportions has a plurality of spaced projecting portions connected theretoand extending therefrom toward the other to form a meander shape. Ameander-shaped charge transfer area is bounded by the band-shapedportions. The charge transfer area forming a charge transfer route has apair of spaced opposite ends and sides including the projecting portionsof the charge transfer area. Each of a plurality of signal extractingmeans is in a corresponding projecting portion of the charge transferarea. Each of the signal extracting means extracts a signal from thecorresponding projecting portion of the charge transfer area. Aplurality of weighting circuits provide a weighting coefficient toextracted signals. Each of the weighting circuits is connected to acorresponding one of the signal extracting means. A signal input isprovided at one end of the charge transfer area. A signal output isprovided at the opposite end of the charge transfer area. A filteredsignal output is connected to the weighting circuits. A plurality ofshort channel stop portions extend from each of the band-shaped portionstoward the center of the charge transfer area. Each of the short channelstop portions terminates at a predetermined space from the band-shapedportion toward which it extends. The short channel stop portions arespaced from each other along the length of the substrate and therebyform a meander-shaped charge transfer route in the charge transfer area.A summing circuit is interposed and interconnected between the weightingcircuit and the filtered signal output.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be readily carried into effect, it willnow be described with reference to the accompanying drawings, wherein:

FIG. 1 is a circuit diagram of the electrode arrangement of atwo-dimensional type charge coupled device of the prior art;

FIG. 2 is a circuit diagram of the electrode arrangement of a singleline, two-dimensional type charge coupled device of the prior art;

FIG. 3 is a schematic diagram of an embodiment of the charge coupleddevice of the invention, showing the channel stop pattern;

FIG. 4 is a schematic diagram of the embodiment of FIG. 3, showing thegate electrode pattern and charge transfer route;

FIG. 5a is a cross-sectional view, taken along the lines Va--Va, of FIG.3;

FIG. 5b is a cross-sectional view, taken along the lines Vb--Vb, of FIG.3;

FIG. 5c is a cross-sectional view, taken along the lines Vc--Vc, of FIG.3;

FIG. 6 is a schematic top plan view of an embodiment of thetwo-dimensional type charge coupled device of the invention;

FIGS. 7a, 7b and 7c are cross-sectional views of three differentembodiments of the charge coupled device of the invention;

FIG. 8 is a block diagram explaining the principle of operation of thetransversal filter of the invention;

FIG. 9 is a plan view of an embodiment of the transversal filter of theinvention;

FIG. 10 is a schematic diagram of an embodiment of the imaging device ofthe invention including a regenerative amplifier; and

FIG. 11 is a plan view of the overall embodiment of FIG. 10.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a two-dimensional driving type CCD of the prior arthaving matrix electrodes. The CCD of FIG. 1 has gate electrodes 1a, 1b,1c, 1d, 2a, 2b, 2c, 2d, 3a, 3b, 3c, 3d, 4a, 4b, 4c, 4d, 5a, 5b, 5c, 5d,6a, 6b, 6c and 6d. The gate electrodes form a matrix consisting of rowsand columns. The electrodes of each column are connected to each otherand all the electrodes in each column are kept at the same potential.The columns of the gate electrodes 1a to 1d, the gate electrodes 3a to3d and the gate electrodes 5a to 5d are connected to a bus line 11. Thecolumns of the gate electrodes 2a to 2d, the gate electrodes 4a to 4dand the gate electrodes 6 a to 6d are connected to the bus line 12.

When pulse trains having different phases are applied respectively toinput terminals P1 and P2 connected to the bus lines 11 and 12,respectively, charge transfer is carried out. In this case, chargetransfer is always performed in the direction shown by the arrow 13,that is, the direction in each row, and is not performed in thedirection in each column. Furthermore, since half the gate electrodesare connected to each bus line, just half the total capacitancegenerated between each electrode and the substrate is loaded on theclock pulse generator which generates the pulse trains to be applied tothe bus lines. It is a disadvantage that all the gate electrodes of theother rows are loaded on the clock pulse generator, even if the transferis necessary only at one row. Attempts to avoid this disadvantage resultin at least one bus line for each row. As a result, the wiring patternbecomes complicated and the integration density is also degraded.

As is obvious from FIG. 2, a CCD of single line type also requires twobus lines 11 and 12 in addition to gate electrodes 21, 22, 23, 24, 25,26, 27 and 28 for transfer. The capacitance of the bus line is notnegligible compared with the capacitance of the gate electrodes, ashereinbefore described.

FIG. 3 is a plan view of an embodiment of the CCD of the invention. InFIG. 3, the semiconductor substrate surface area 32 between parallelextending channel stops 30 and 31 in the shape of bands corresponds tothe area in which the charge transfers, that is, the channel. Thechannel stops 30 and 31 have no simple band shape, but short portions30a and 31a projecting toward the center of the channel 32. The shortportions are interdigitated. The provision of such a pattern for thechannel stops, results in a meandering charge transfer path, indicatedby a line 33 with arrow heads thereon. The charge transfer mechanism ishereinafter described.

The broken line in FIG. 3 indicates the shape and position of gateelectrodes A and B which are strip-shaped and extend linearly. PortionsPA and PB of the gate electrodes are terminals for connection. Althoughit is not shown in FIG. 3, the gate electrodes A and B are separatedfrom the substrate by an insulating film, such as, for example, silicondioxide film, SiO₂. The SiO₂ film is non-uniform in thickness, and ishereinafter described. In the embodiment of FIG. 3, the parallelportions 30 and 31 of the channel stop are coupled as shown by 34 at theleft end. The coupling is provided in order to partition the left end ofthe channel 32. There is no need for such a coupling when the left partis the end of the substrate.

The charge transfer mechanism of the embodiment of FIG. 3 is explainedwith reference to FIG. 4. In FIG. 4, the gate electrodes A and B areshown by solid lines and the edges of the channel stop are shown bybroken lines. In FIG. 4, a two phase clock pulse generator 40 isconnected to the terminals PA and PB. The clock pulse generator 40generates two square pulse trains, having a phase difference of a halfperiod or π radian between them, as the clock pulse for transfer.

As hereinbefore described, the thickness of the SiO₂ film under the gateelectrodes is non-uniform in the embodiment of FIGS. 3 and 4. For a moreaccurate presentation, the portion of the insulating film which isthinner than the remainder thereof is shaded in FIG. 4. Furthermore, theconductivity type of the substrate is assumed to be p type forconvenience. The polarity of the clock pulse is therefore assumed to bepositive. In order to distinguish different parts of the channel 32 fromeach other, each of the small areas sandwiched by two short channelstops which are adjacently arranged under the same gate electrodes ishereinafter referred to as a cell. The right half and the left half ofeach cell is hereinafter referred to as a half cell. The half cells arenumbered 41, 42, 43, 44, 45, 46, 47, 48 . . .

It is assumed that the potential of the terminal PA is zero, which isthe same potential as the substrate, the potential of the terminal PB ispositive, and the charge to be transferred is stored in the depletionlayer generated under the lower left half cell 41. If the potential ofthe terminal is reversed, and the terminal PA becomes positive, and thepotential of the terminal PB is zero, the charge stored under the halfcell 41 is once transferred to the half cell 42. However, since thedepletion layer formed at the area below the half cell 43 is deeper thanthat under the half cell 41, the charge immediately flows into thedepletion layer under the half cell 43 and is stored there. Then, whenthe potential of the terminals is again reversed, and the potential ofthe terminal PA becomes zero and the potential of the terminal PBbecomes positive, the charge passes the half cell 44 and is transferredto the area under the half cell 45.

The partial difference in the depth of the depletion layer, ashereinbefore mentioned, is based on the unevenness of the thickness ofthe SiO₂ film. In other words, since the depletion layer formed underthe thin SiO₂ film is deeper than that under the thick SiO₂ film, thecharge which has been transferred to the half cell under the thick SiO₂film is naturally moved to the inside of the deeper depletion layer evenif the gate voltage is constant. However, there is no possibility of abackward flow of the charge from the half cell 44 to the half cell 41.This is due to the separation of the half cells from each other by shortchannel stops 31a. As described, the charge to be transferred isadvanced toward the right following the route, indicated by the line 33having the arrow heads, through the channel 32.

The embodiment of FIGS. 3 and 4 performs substantially the same functionas the conventional CCD. The CCD of the invention may thus be used forthe same applications as the conventional CCD, that is, as shiftregisters and imaging devices. Furthermore, the embodiment of FIGS. 3and 4 has no bus line corresponding to the bus lines 11 and 12 of theconventional CCD, and the electrodes A and B are simple straight strips.For this reason, the electrostatic capacitance loaded on the clock pulsegenerator 40 is considerably less compared to that of the conventionalCCD.

FIGS. 5a, 5b and 5c are sectional views of three different embodimentsof the CCD of the invention, as hereinbefore described. FIG. 5a is asectional view, taken along the lines Va--Va, of FIG. 3, FIG. 5b is asectional view, taken along the lines Vb--Vb, of FIG. 3. FIG. 5c is asectional view, taken along the lines Vc--Vc, of FIG. 3. The broken lineinside the semiconductor substrate S in FIG. 5c shows the forming of thedepletion layer caused in the substrate when a transfer voltage isapplied to the gate electrode B, for example, and the depletion layerformed at the portion under the thin SiO₂ film 60 is deeper than theremainder of the film, as shown in FIG. 5c.

FIG. 6 shows an embodiment of the two-dimensional type charge coupleddevice of the invention. In FIG. 6, the CCD has channel stops 301, 302,303, 304, . . . , gate electrodes A1, A2, A3, . . . and B1, B2, B3, . .. , and channels 61, 62, 63, 64, 65, . . . As is readily evident fromFIG. 6, each electrode may easily be electrically independent.Furthermore, electrodes of the necessary number may also be connected inparallel very easily.

Therefore, the electrodes A1, A2, A3, . . . and B1, B2, B3, . . . , forexample, are connected in parallel, respectively, and these electrodesmay be divided into two groups, Additionally, the voltage may be appliedonly to the selected electrode, without complicated multilayeredwirings. These advantages are very useful for line addresses.

The charge coupled device of the invention may be modified for variousapplications in addition to the embodiments hereinbefore described. Suchmodifications are hereinafter described.

In the embodiments of FIGS. 3 and 6, the charge transfer route isextended in a meandering direction, and such charge transfer directionmay be changed half way, as required, at any angle. This may be done bybending the channel stops 30 and 31 in FIG. 3 at the desired angle andsimultaneously bending the gate electrodes A and B at the same angle asthe channel stops.

In FIG. 3, the channel stops 30 and 30a extend at right angles to eachother. However, the angle formed by the channel stops may be changedfreely. Furthermore, although the short channel stops 30a extend fromthe longer channel stop 30 in FIG. 3, a gap, if it is narrow, may beformed between each channel stop 30a and the channel stop 30. Gaps mayalso be provided between each channel stop 31a and the channel stop 31.

A semiconductor, such as silicon or gallium arsenide, may be used as thegate electrode and a conductive metal oxide, such as tin oxide, may beused in addition to a metal, such as aluminum, chromium, silver, or thelike. Furthermore, as a countermeasure for the potential barrier whichis often caused under a gap between a pair of next-adjacent gateelectrodes, it is recommended that the gap be filled with a highresistivity material, or that a third electrode be formed on the gap,but insulated from the gate electrode.

FIGS. 7a, 7b and 7c illustrate three ways for preventing the formationof the potential barrier. In FIGS. 7a, 7b and 7c, the CCD has gateelectrodes A and B and channel stops 30 and 31. In FIGS. 7a, 7b and 7c,p, n, p⁺, p⁻ are the conductivity type and resistivity of eachsemiconductor. The symbol p⁺ indicates a p conductivity type having alow resistivity or high impurity concentration, while the symbol p⁻indicates a p conductivity type having a high resistivity or lowimpurity concentration.

In FIG. 7a, a conductive layer 71 is formed between the gate electrodesA and B. The conductive layer 71 is separated from both gate electrodesby an insulative or insulating film 72.

In FIG. 7b, an n conductivity type layer 73 is formed under a gap gbetween the gate electrodes A and B. In FIG. 7c, the gap g is filled bya semiconductor layer 74 of high resistivity.

In FIGS. 7a, 7b and 7c, the p conductivity type layer 70, which has alittle higher impurity concentration than the substrate, is provided inthe channel. The p conductivity type layer 70 is provided for guidingthe charge, and this makes it unnecessary to provide a partialdifference of thickness to the SiO₂ film.

The CCD of the invention makes it easy to extract the signal which istransferred as the charge from the side of the channel and to providesome processing, based on the unique charge transfer mechanism, of theshape and arrangement of the gate electrodes. In this case, acomplicated crossover technique is not required.

FIG. 8 is a block diagram for explaining the principle of operation ofthe transversal filter. In FIG. 8, a total of n delay lines 81a, 81b,81c to 81n are connected in series and the taps are extracted from thejoints of each delay line. The signal to be filtered is applied to aninput terminal 84. Weighting coefficients a1, a2, a3 to an arerespectively multiplied to the voltages S1, S2, S3 and Sn appearing ateach tap via a weighting circuit group 82. The outputs of the weightingcircuit group 82 are connected to a total summing circuit 83. The outputvoltage Vout appears at the output terminal 85.

The output voltage is defined as ##EQU1## Therefore, when the delay timeof one stage is assumed to be td, ##EQU2## wherein Vin is the inputvoltage.

The Fourier transform of the right term becomes ##EQU3##

The transfer function of the circuit, that is, the transfer functionbetween the input terminal and the output terminal for the signal afterprocessing is therefore almost equal to H(ω). That is, the circuit ofFIG. 8 has substantially the same function as a filter having afrequency characteristic of H(ω). The transversal filter of theinvention utilizes the CCD as the aforedescribed delay lines.

FIG. 9 shows the major part of an embodiment of the transversal filterof the invention. In the embodiment of FIG. 9, projecting portions 90a,90b, 90c, 90d to 90n are provided at the channel stop 90, and reverseconductivity layers D1, D2, D3 to Dn are formed in each projectingportion. The signal is extracted from each of the projecting portions90a to 90n. Weighting is provided by weighting circuits W1, W2, W3 toWn. An input terminal 92 provides the signal to be filtered. An outputterminal 93 provides the signal which has passed the CCD and a filteroutput terminal 94 provides the filtered signal. The output signal atthe filter output terminal has the desired frequency spectrum and saidsignal is applied to an external circuit, if required.

Opposite conductivity type layers Do and Dn are provided for the inputand output, respectively, of the signal. A total summing circuit 95 isprovided. The line with the arrow heads thereon indicates the route viawhich the charge is transferred. The gate electrodes A and B are similarto those of FIG. 3. Although the projecting portions 90a to 90n areprovided for each stage in the embodiment of FIG. 9, they may beprovided for each desired stage.

As is obvious from FIG. 9, any projecting portion is not covered by thegate electrodes A and B. Therefore, it is obvious that the wiring forapplying the signal extracted from the reverse conductivity layers D1,D2, D3 to Dn and supplied to the weighting circuits W1, W2, W3 to Wn,does not cross either of the gate electrodes. The crossover technique isthus not required.

The CCD of the invention, with a meandering channel may easily branchthe signal to the side of the channel, as hereinbefore mentioned. Forthis reason, when a transfer to a plurality of stages is required,signal loss due to transfer may be compensated by amplifying the signalextracted to the side of the channel and then returning it to thechannel again.

FIG. 10 shows a portion of the arrangement of the invention for signalextraction and regeneration by amplification. In FIG. 10, interdigitatedchannel stops 114 and 115 have projecting portions 114a and 115a. Inaddition, a projecting portion 115b is provided at the side of thechannel stop 115 and a reverse conductivity layer 121, for signal inputand output, is formed inside the portion 115b. The extracted signalcharge is amplified by a regenerative amplifier 122 and the amplifiedsignal charge is returned to the reverse conductivity type layer 121.Thereafter, as described with reference to FIG. 4, the signal istransferred along the meandering route by means of the clock pulseapplied to the gate electrodes 112 and 113.

A signal control gate electrode 123 controls the signal input and outputand is called the signal control gate electrode to distinguish it fromthe gate electrodes 112 and 113 for charge transfer. In FIG. 10, thesignal control gate electrode 123 opens when the regeneration amplifier122 receives the input signal. However, the signal control gateelectrode 123 may also be controlled by the transfer clock pulse.

FIG. 11 is a single line imaging device of the invention. In FIG. 11,the substrate area covered with a photo gate electrode 131 is aphotosensitive area, except for the channel stop 134. The photosensitivearea provides the photoelectric conversion function. When thephotosensitive area is irradiated by light, the generated charge, thatis, the mobile carrier, is controlled by ON/OFF gate electrodes 132a and132b. When a voltage is applied to each ON/OFF gate electrode 132a and132b, the generated charge enters the charge transfer portion and istransferred by transfer gates 133a and 133b. Thereafter, the charge maybe extracted from the output terminal 137 at the right hand side.

The charge generated by the incident light shifts the charge transferarea under the electrodes 132a and 132b on both sides, respectively, viathe transfer gates 133a and 133b. Furthermore, the charge is transferredalong the meandering route by the voltage applied to the gate electrodes132a and 132b. The channel stop of FIG. 11 corresponds to the channelstops 30 and 31 of FIG. 3.

The imaging device of FIG. 11 has reverse conductivity type layers 135and 138 for signal extraction and a regenerative amplifier 136. As isclear from FIG. 11, the imaging device of the invention does not requirea bus line for applying a clock pulse, and therefore, the substrate areaoccupied is small, so that the device is designed very compactly as awhole.

As may be understood from the foregoing explanation, the CCD of theinvention may greatly simplify the shape of the transfer (gate)electrodes on the basis of the shape of the unique channel stop patternand charge transfer mechanism. As a result, almost every bus line forfeeding the clock pulse to the gate electrode may be eliminated. Thisnot only results in high integration density, but also simplifies themanufacturing process. Furthermore, signals are easily extracted fromand injected into the channel side without a crossover technique. Thetransversal filter of the invention may thus provide wiring for theweighting circuit without crossover. On the other hand, the imagingdevice of the invention does not require the establishment of a bus lineoutside the channel and may be of compact configuration for the entiredevice including the regenerative amplifier.

While the invention has been described by means of specific examples andin specific embodiments, I do not wish to be limited thereto, forobvious modifications will occur to those skilled in the art withoutdeparting from the spirit and scope of the invention.

I claim:
 1. A charge coupled device having a semiconductor substrate ofpredetermined conductivity type, said substrate having a surface, a pairof substantially band-shaped channel stops formed on the substratesurface and extending in spaced substantially parallel relation, saidchannel stops comprising a high impurity concentration layer of thepredetermined conductivity type formed on said substrate surface, acharge transfer area of a uniform conductivity type bounded by theband-shaped channel stops, a plurality of short channel stopsalternately extending from each of the band-shaped channel stops towardthe center of the charge transfer area, each of the short channel stopsterminating at a predetermined space from the opposing band-shapedchannel stop, the short channel stops comprising the high impurityconcentration layer of the predetermined conductivity type formed onsaid substrate surface in an interdigitated pattern with the channelstops, a plurality of cells each comprising a small area betweennext-adjacent short channel stops of a corresponding one of theband-shaped channel stops, said cells being staggered along said chargecoupled device, means for forming an asymmetrical depletion layer ineach of said cells in a regular arrangement to determine a transferdirection of the charge, a film of electrically insulative materialcovering the charge transfer area, and a pair of elongated substantiallystraight parallel gate electrodes over said insulative film, one of saidgate electrodes commonly covering the cells of one of the band-shapedchannel stops and the other of said gate electrodes commonly coveringthe cells of the other of the band-shaped channel stops thereby forminga single directional meander-shaped charge transfer channel of saiduniform conductivity type in the charge transfer area under said pair ofgate electrodes free from any other electrode, said gate electrodeshaving a side; anda signal device at the side of said gate electrodesand providing a connection path for a signal charge through said one ofsaid band-shaped channel stops, thereby eliminating electrode crossover.2. A charge coupled device as claimed in claim 1, wherein said substratehas a depletion area and said insulative film has a non-uniformthickness, said depletion area having a depth determined by thenon-uniformity in thickness of said depletion layer, the depletion layerunder the thinner portion of said film being deeper than that under thethicker portion of said film whereby a charge transferred to the halfcell under said thicker portion is moved to the inside of the deeperdepletion layer notwithstanding a constant gate voltage.